1. Field of the Invention
This invention relates to a method for processing a hydrogen sulfide and ammonia mixture to produce hydrogen and sulfur.
2. Description of the Prior Art
In many industrial processes, streams of acid gases are produced. Streams commonly referred to as acid gas streams typically contain hydrogen sulfide and may contain other sulfur compounds. In many instances, these streams may also include ammonia.
Acid gas streams are typically processed in Claus units wherein the hydrogen sulfide is partially oxidized to produce a hydrogen sulfide/sulfur dioxide mixture in a proper ratio for reaction of the hydrogen sulfide and sulfur dioxide to produce elemental sulfur and water. As a first step in such Claus processes, the acid gas stream is burned to produce the desired quantity of sulfur dioxide in a burner system.
When substantial amounts of ammonia are present in the stream, the combustion of the mixed stream of hydrogen sulfide and ammonia in the burner system results in excessively high temperatures, i.e. as high as 2900.degree. F. Desirably, the temperature in most burner systems is kept below 2800.degree. F. and preferably below 2600.degree. F. Further, the combustion of the ammonia and hydrogen sulfide in the burner system at the elevated temperatures results in the production of NO.sub.x, sulfur trioxide, and related compounds. The NO.sub.x compounds are an undesirable environmental pollutant and their emission must be limited. The sulfur trioxide is a compound which condenses at relatively low temperatures and reacts readily with water to form an acid. This acid is extremely corrosive and may be damaging to downstream equipment which operates at a temperature below the condensation temperature of sulfur trioxide. Further, some of the sulfurous compounds are reactive with any unreacted ammonia to form sulfur-ammonia compounds which are also undesirable in the system which is designed to handle gaseous streams, except for the liquid sulfur stream typically recovered from a Claus unit.
It is immediately apparent that both the hydrogen sulfide and the ammonia contain large amounts of hydrogen which are desirably recovered. Accordingly, it is desirable that a process be available wherein the ammonia can be fully reacted to produce environmentally acceptable materials and hydrogen and wherein the sulfur can be combusted and passed to a Claus unit without the production of undesirable acids or solid materials as by-products.